TW201710723A - Resin optical waveguide - Google Patents

Abstract

A resin optical waveguide is provided with a core, under-cladding having a lower refractive index than the core, and over-cladding. The resin optical waveguide is characterized in that a core exposure section in which the core is exposed and the over-cladding is not present is provided to one end side of the resin optical waveguide. The resin optical waveguide is also characterized by comprising a core vicinity area in which the part of the under-cladding corresponding to the core exposure section satisfies the conditions (1) and (2) indicated below. (1) The core vicinity area is an area within a distance x from the core and x is 5-20 [mu]m. (2) The core vicinity area has a refractive index distribution in which the refractive index on the interface side with the core is higher and the refractive index on the distal side with respect to the interface with the core is lower.

Description

Resin optical waveguide

The present invention relates to a resin optical waveguide.

Non-patent documents 1, 2, and 1 are proposed to have a low-loss and low-cost connection of a photonic interface between a krypton waveguide and a resin optical waveguide. The term "boring waveguide" as used in the present specification means a structure in which a core cladding layer functioning as a (single mode) optical waveguide is formed on a germanium wafer.

Fig. 3 is a perspective view showing a configuration example of such a bismuth photo interface, and Fig. 4 is a side view thereof.

One or a plurality of resin optical waveguides 310 are formed in the resin optical waveguide wafer 300 shown in Figs. On one end side of the resin optical waveguide wafer 300, the resin optical waveguide 310 is connected to a pupil waveguide (not shown) formed on the calender waveguide wafer 200. The other end side of the resin optical waveguide wafer 300 is housed in the connector 100.

Fig. 5 is a perspective view showing a configuration example of one of the resin optical waveguides used for the above purpose.

The resin optical waveguide 310 shown in FIG. 5 is provided with a lower cladding layer 330 and an upper cladding layer 340 around the core 320. However, in FIGS. 3 and 4, the front end connected to the pupil optical waveguide (not shown) formed on the neon waveguide wafer 200 is a core in which the upper cladding layer 340 is not disposed and the core 320 is exposed to the outside. The body exposed portion 350.

Fig. 6 is a cross-sectional view showing a connection portion between the pupil waveguide 210 and the resin optical waveguide 310 in the bismuth photo interface shown in Figs. 3 and 4, and the resin optical waveguide 310 is a resin optical waveguide 310 shown in Fig. 5. In FIG. 6, the pupil waveguide 210 and the resin optical waveguide 310 are in the resin optical waveguide 310. The state in which the core 320 faces the calender waveguide 210 is connected using an epoxy resin.

Figure 7 is a schematic view for explaining the transmission of light in the photonic interface shown in Figures 3 and 4. In FIG. 7, light is transmitted from the core 220 of the optical waveguide 210 to the core 320 exposed at the front end of the resin optical waveguide 310 by adiabatic coupling. Light is then transmitted from the core 320 of the resin optical waveguide 310 to the core 140 of the optical fiber 130.

[Previous Technical Literature] [Non-patent literature]

Non-Patent Document 1: Jie Shu, Ciyuan Qiu, Xuezhi Zhang, and Qianfan Xu, "Efficient coupler between chip-level and board-level optical waveguides", OPTICS LETTERS, Vol.36, No. 18, pp3614-3616 (2011)

Non-Patent Document 2: Tymon Barwics, and Yoichi Taira, "Low-Cost Interfacing of Fibers to Nanophotonic Waveguides: Design for Fabrication and Assembly Toleranes", IEEE Photonics Journal, Vol.6, No. 4, August, 660818 (2014)

[Patent Literature]

Patent Document 1: US Patent No. 8,724,937

The resin optical waveguide 310 shown in Fig. 5 was subjected to the same procedure as the previous resin optical waveguide before the mounting of the photonic interface shown in Figs. In the performance evaluation of the resin optical waveguide, a single mode fiber is connected to the front end of the resin optical waveguide. Fig. 8 is a schematic view for explaining the propagation of light when a single mode fiber is connected to the front end of the resin optical waveguide 310 shown in Fig. 5. In the connection between the resin optical waveguide 310 and the single-mode optical fiber 400 shown in FIG. 5, there is a problem that a part of the light is not transmitted after being radiated from the portion where the core 320 at the front end of the resin optical waveguide 310 is exposed, and connection loss occurs. This connection loss did not occur when mounted on the 矽 photonic interface shown in Figs. 3 and 4, and the reliability of the performance evaluation result was lowered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a resin optical waveguide which is suitable for low-loss and low-cost connection of a germanium photonic interface of a krypton waveguide and a resin optical waveguide, and which uses the performance of a single mode fiber in order to solve the problems of the prior art described above. The reliability of the evaluation is high.

In order to achieve the above object, the present invention provides a resin optical waveguide characterized in that it has a core body and a refractive index lower than a cladding layer and an upper cladding layer of the core body, on one end side of the resin optical waveguide. a core exposed portion in which the upper cladding layer is not present to expose the core, and a portion corresponding to the core exposed portion of the lower cladding layer has a region near the core (1) and (2) (1) The region in the vicinity of the core is a region within a distance of x from the core, and x is 5 μm or more and 20 μm or less; (2) the region near the core has a refractive index distribution: The refractive index at the interface side is high, and the refractive index on the far side of the interface with the core is lowered.

In the resin optical waveguide of the present invention, it is preferable that the length of the core exposed portion in the light transmission direction is 100 μm or more.

In the resin optical waveguide of the present invention, it is preferable that the refractive index distribution in the vicinity of the core is 0.00004 / μm or more.

In the resin optical waveguide of the present invention, it is preferable that a difference (n _max -n _min ) between the maximum value n _max and the minimum value n _min of the refractive index of the lower cladding layer in the vicinity of the core is 0.0001 or more. .

In the resin optical waveguide of the present invention, it is preferable that a difference between a maximum value n' _max of the refractive index in the core body and a maximum value n _max of a refractive index of the lower cladding layer in the vicinity of the core body ( n' _max -n _max ) is 0.008 to 0.02.

In the resin optical waveguide of the present invention, preferably, in a portion of the lower cladding layer corresponding to the exposed portion of the core, a refractive index of a portion other than the vicinity of the core is the above-mentioned region in the vicinity of the core The minimum value of the refractive index of the lower cladding layer is less than or equal to n _min .

In the resin optical waveguide of the present invention, it is preferable that the thickness of the lower cladding layer is 10 μm or more.

The resin optical waveguide of the present invention is preferably a single mode optical waveguide at least one of a wavelength of 1310 nm and a wavelength of 1550 nm.

In the resin optical waveguide of the present invention, it is preferable that the resin optical waveguide has a core size of 1 to 10 μm.

In the resin optical waveguide of the present invention, it is preferable that the core of the resin optical waveguide contains a resin containing fluorine.

Moreover, the present invention provides a resin optical waveguide characterized in that it has a core body and a cladding layer having a lower refractive index than the lower cladding layer and the upper cladding layer, and is provided on one end side of the resin optical waveguide. The core body and the core exposed portion of the cladding layer adjacent to the core body are exposed without the upper cladding layer, and the length of the core exposed portion of the resin optical waveguide in the light transmission direction is 500 μm or more, and the above-mentioned under package The portion corresponding to the core exposed portion in the coating layer has a region in the vicinity of the core body satisfying the following (1) to (3): (1) a region in the vicinity of the core body from the core body within a distance of x, x is 10 μm or more and 20 μm or less; (2) the vicinity of the core has a refractive index distribution: a refractive index higher on the interface side with the core, and a refractive index on the far side from the interface with the core (3) The difference (n _max -n _min ) between the maximum value n _max and the minimum value n _min of the refractive index of the lower cladding layer in the vicinity of the core is 0.001 or more.

Preferably, the resin optical waveguide of the present invention is connected to the calender waveguide at the core exposed portion.

The resin optical waveguide of the present invention is suitable for connecting a quenched waveguide with low loss and low cost The photon interface with the resin optical waveguide.

The resin optical waveguide of the present invention has a small connection loss when evaluating the performance of a single-mode optical fiber, and has high reliability in performance evaluation.

10‧‧‧Resin Optical Waveguide

11‧‧‧ core

12‧‧‧Under cladding

13‧‧‧Upper coating

14‧‧‧ Core Exposed

100‧‧‧Connector

130‧‧‧Fiber

140‧‧‧ core

200‧‧‧Lightguide waveguide chip

210‧‧‧矽光光

220‧‧‧ core

230‧‧‧covered

300‧‧‧Resin Optical Waveguide Wafer

310‧‧‧Resin Optical Waveguide

320‧‧‧ core

330‧‧‧Under cladding

340‧‧‧Upper coating

350‧‧‧ core body

400‧‧‧ single mode fiber

410‧‧‧ core

420‧‧ ‧ coating

Fig. 1 is a perspective view showing a configuration example of a resin optical waveguide of the present invention.

Fig. 2 is a schematic view showing a connection portion between a resin optical waveguide and a single mode optical fiber in the embodiment.

Fig. 3 is a perspective view showing a configuration example of a photon interface.

Figure 4 is a side view of the photonic interface of Figure 3.

Fig. 5 is a perspective view showing a configuration example of a resin optical waveguide used for the photon interface of Figs. 3 and 4.

Fig. 6 is a cross-sectional view showing a connection portion between the pupil waveguide and the resin optical waveguide 310 formed on the 波导-waveguide wafer 200 in the 矽 photonic interface shown in Figs.

Figure 7 is a schematic view for explaining the transmission of light in the photonic interface shown in Figures 3 and 4.

Fig. 8 is a schematic view for explaining the propagation of light when a single mode fiber is connected to the front end of the resin optical waveguide 310 shown in Fig. 5.

Hereinafter, the present invention will be described with reference to the drawings.

Fig. 1 is a perspective view showing a configuration example of a resin optical waveguide of the present invention. The resin optical waveguide 10 shown in FIG. 1 is provided with a core 11 and a cladding layer 12 and an upper cladding layer 13 having a lower refractive index than the core 11. A lower cladding layer 12 is disposed below the core 11 , and an upper cladding layer 13 is disposed above the core 11 . However, the core exposed portion 14 in which the upper cladding layer 13 is absent and the core 11 is exposed is provided on one end side of the resin optical waveguide 10.

Further, in the resin optical waveguide of the present invention, the side of the cladding layer and the upper cladding layer which are disposed under the core is not present on the exposed portion of the core as the upper cladding layer. Therefore, it can also The lower cladding layer is disposed above the core body, and the upper cladding layer is disposed under the core body.

The core exposed portion 14 serves as a connection portion with the pupil waveguide when the resin optical waveguide 10 is used as a photonic interface. Therefore, the core exposed portion 14 is required to have a length sufficient to serve as a connection portion with the calender waveguide. The resin optical waveguide 10 of the present invention preferably has a length of the core exposed portion 14 in the light transmission direction of the resin optical waveguide of 100 μm or more, which is sufficient for the length of the connection portion with the calender waveguide. In addition, the light transmission direction of the resin optical waveguide refers to the long axis direction of the core 11.

The length of the resin optical waveguide of the core exposed portion 14 in the light transmission direction is more preferably 300 μm or more, further preferably 500 μm or more, and still more preferably 1,000 μm or more.

However, if the length of the core exposed portion 14 in the light transmission direction of the resin optical waveguide is too long, when an adhesive (for example, an epoxy resin) is used to connect with the calender waveguide, the connection loss may be changed by absorption of the adhesive. Big one. Therefore, the length of the core exposed portion 14 in the light transmission direction of the resin optical waveguide is preferably 10000 μm or less, more preferably 5,000 μm or less, and still more preferably 3,000 μm or less.

In the resin optical waveguide 10, the lower cladding layer 12 and the upper cladding layer 13 have a refractive index lower than that of the core 11 because the light propagating in the core 11 is prevented from being coated on the side of the cladding layer 12 or on the upper side. The layer 13 is radiated.

As described above, when the resin optical waveguide 310 having the core exposed portion and the single-mode optical fiber 400 are connected as shown in FIG. 8, the core exposed portion of the upper cladding layer 340 is not present, and the core 320 is exposed. . Since the performance evaluation of the resin optical waveguide 310 is performed in a state where the exposed portion of the core is present in the air or in water, the exposed surface of the core 320 is in contact with air or water, but the refractive index of the air or water is smaller than that of the resin optical waveguide 310. The material of the core 320 or the material of the lower cladding layer 330. As a result, a portion of the light transmitted in the core 320 is radiated toward the side of the cladding layer 330, resulting in a connection loss.

In the resin optical waveguide 10 of the present invention, the portion corresponding to the core exposed portion 14 of the lower cladding layer 12 has a region in the vicinity of the core that satisfies the following (1) and (2), thereby suppressing the single-mode light. Connection loss when the fiber is connected.

(1) The region in the vicinity of the core is a region in which the distance from the core 11 is within x, and x is 5 μm or more and 20 μm or less.

(2) The vicinity of the core has a refractive index distribution in which the refractive index on the interface side with the core 11 is higher, and the refractive index on the far side from the interface with the core 11 becomes lower.

By providing a refractive index distribution in which the refractive index on the proximal side of the core 11 is higher and the refractive index on the distal side of the core 11 is lower in the vicinity of the core, the core exposed portion 14 can be suppressed to the core 11 The transmitted light is radiated to the side of the cladding layer 12, and the connection loss at the time of connection with the single mode fiber can be suppressed. Further, the refractive index distribution in the above (2) is generated by continuously decreasing the refractive index from the interface side with the core 11 toward the distal side with respect to the interface with the core 11.

Here, the region in the vicinity of the core is a region in which the distance from the core 11 is within x, and x is set to 5 μm or more, whereby the light emitted from the core 11 is suppressed from being discharged to the core exposed portion 14. The coating 12 is radiated on the side. In addition, the reason why the upper limit of x is 20 μm is that the refractive index distribution is provided in a region where the distance from the core 11 is 20 μm or more, and the effect of suppressing the connection loss when connecting to the single-mode optical fiber is facilitated. Also less.

In the resin optical waveguide 10 of the present invention, in terms of the effect of suppressing the connection loss when the single-mode optical fiber is connected, the refractive index distribution in the vicinity of the core is preferably 0.00004 / μm or more.

The refractive index distribution in the vicinity of the core is preferably 0.0007 / μm or more, more preferably 0.000075 / μm or more, further preferably 0.0001 / μm or more, and particularly preferably 0.0002 / μm or more.

In addition, the upper limit of the refractive index distribution is not particularly limited, and may be, for example, 0.00035 by the following production method or the like.

Regarding the refractive index of the lower cladding layer 12 in the vicinity of the core, the refractive index with respect to the proximal side of the core 11 becomes the maximum value n _max , and the refractive index with respect to the far side of the core 11 becomes the minimum value n _Min . The difference between the maximum value of the refractive index n _max of the lower cladding layer 12 in the vicinity of the core and the minimum value n _min (n _max -n _min ) in terms of the connection loss when the connection to the single mode fiber is suppressed. It is preferably 0.0001 or more, more preferably 0.0002 or more, still more preferably 0.0004 or more, and still more preferably 0.0008 or more.

In addition, the upper limit of the difference between the maximum value n _{max of the} refractive index and the minimum value n _min is not particularly limited, and may be, for example, 0.0035 by the following production method or the like.

The maximum value of the refractive index n' _max in the core 11 and the lower portion in the vicinity of the core are considered in terms of suppressing the connection loss with the boring waveguide and suppressing the connection loss when connecting to the single mode fiber. the difference between the maximum value n _max (n _'max -n _max) of the refractive index of the cladding layer 12 is preferably 0.008 to 0.02. Here, n is set to the maximum value of the refractive index of the core 11 in the _'max in that reason, in consideration of the refractive index profile of the core of the case 11 is also present.

More preferably, n' _max -n _max is 0.010 to 0.015.

In the resin optical waveguide of the present invention, in terms of suppressing the connection loss at the time of connection with the single-mode optical fiber, it is preferable that the portion of the lower cladding layer 12 corresponding to the vicinity of the core in the portion corresponding to the exposed portion of the core is parts of the refractive index of the core region near the body under cladding layer refractive index n _min of the minimum value of 12 or less. The refractive index of the coating layer 12 other than the region in the vicinity of the core is not particularly limited as long as it is equal to or less than the minimum value n _min . Therefore, the refractive index of the portion other than the region in the vicinity of the core may be all the same value, and may have a refractive index which is further lowered toward the far side with respect to the core 11 as in the case of the vicinity of the core. Rate distribution.

Further, in the resin optical waveguide of the present invention, depending on the thickness of the lower cladding layer 12, the entire portion of the lower cladding layer 12 corresponding to the exposed portion of the core may satisfy the above (1), (2), preferably. In order to satisfy the area near the core of the above (1) to (3). In this case, the thickness of the lower cladding layer 12 coincides with the above x.

Further, in the resin optical waveguide of the present invention, the refractive index of the cladding layer 12 under the portion where the upper cladding layer 13 and the lower cladding layer 12 are disposed above and below the core 11 is included as long as the core is attached. The area including the near region is a value lower than the refractive index of the core 11, and is not particularly limited. Therefore, for example, regarding the cladding layer 12 under the portion, the refractive index may be all the same value, or may have a refractive index distribution which is lower toward the far side of the core 11 and lower in refractive index. Further, it may have the same area as the vicinity of the core body satisfying the above (1) to (3).

The resin optical waveguide of the present invention is further described.

(core 11)

In the resin optical waveguide 10 shown in FIG. 1, the cross-sectional shape of the core 11 is rectangular, but is not limited thereto, and may be, for example, a trapezoidal shape, a circular shape, or an elliptical shape. When the cross-sectional shape of the core 11 is a polygon, the angle may be curved.

The core size is not particularly limited, and may be appropriately designed in consideration of coupling efficiency with a light source or a light receiving element. The coupling efficiency depends on the core diameter and numerical aperture (NA). Regarding, for example, the core size of the core 11 (when the cross-sectional shape of the core 11 is a rectangle as shown in FIG. 1 , the width and height of the rectangle), when considering the use as a photonic interface, The coupling efficiency of the optical waveguide to be connected is preferably 1 to 10 μm. More preferably, it is 1.5 to 8 μm, and further preferably 2 to 7 μm. Here, the width of the rectangle is the length of the width at the center of the height, and the height of the rectangle is the length of the height at the center of the width. Furthermore, the core size can also be tapered in the direction of light transmission of the resin optical waveguide.

The core 11 may also have a refractive index profile that is directed toward the distal side with respect to the center of the core and whose refractive index is lowered. Further, the refractive index distribution having a higher refractive index on the upper cladding layer side and lower refractive index on the lower cladding layer side may have a lower refractive index on the upper cladding layer side and a lower cladding layer side. A refractive index distribution in which the refractive index becomes high.

(upper cladding layer 13)

The numerical value of the refractive index of the upper cladding layer 13 is not particularly limited as long as it is lower than the refractive index of the core 11. Therefore, for example, the upper cladding layer 13 may have a numerical value having the same refractive index, and may be configured such that the refractive index becomes lower toward the distal side with respect to the core 11 or may be configured to face the distal position with respect to the core 11 . The refractive index becomes higher on the side.

The thickness of the upper cladding layer 13 is not particularly limited. When the resin optical waveguide 10 of the present invention is a single-mode optical waveguide, the transmitted light is also leaked to a package located within a range of about 10 μm from the center of the core 11. The condition of the cladding part. Therefore, in the case of a single-mode optical waveguide, from the viewpoint of reducing the transmission loss of light, it is preferably 10 μm or more. Further, the total thickness of the lower cladding layer 12 and the upper cladding layer 13 is preferably 20 to 90 μm, more preferably 30 to 70 μm.

In the resin optical waveguide of the present invention, the constituent materials of the core 11, the lower cladding layer 12, and the upper cladding layer 13 are not particularly limited as long as they satisfy the required characteristics as a resin optical waveguide. The constituent material of the core 11 is preferably a resin containing fluorine, from the viewpoint of suppressing the loss of light transmitted in the core 11.

Further, the constituent materials of the core 11, the lower cladding layer 12, and the upper cladding layer 13, and the manufacturing procedure of the resin optical waveguide can be referred to, for example, the following documents.

International Publication No. 2010/107005

Japanese Patent Laid-Open Publication No. 2013-120338

Japanese Patent Laid-Open No. 2012-63620

When the resin optical waveguide 10 of the present invention shown in Fig. 1 is produced as a reference, the core exposed portion 14 of the resin optical waveguide 10 can be formed by the following procedure.

Forming a lower cladding layer, forming a core on the lower cladding layer by a photolithography process, applying a cured composition on the lower cladding layer and the core, and curing the resin by heating and/or light irradiation The composition hardens to form an upper coating. When the upper cladding layer is formed, a region having the upper cladding layer and a region where the upper cladding layer is absent to expose the core (i.e., the core exposed portion) can be formed by using a photolithography process.

Further, the coating layer 12 having a region in the vicinity of the core body satisfying the above (1) and (2) can be formed by the following procedure.

By adjusting the heating temperature or heating time when forming the lower cladding layer, and/or by adjusting the irradiation intensity or the irradiation time of the light, it is possible to form the above (1), (2), and It is preferable to satisfy the cladding layer 12 under the vicinity of the core of the above (1) to (3). Alternatively, it may be adjusted by adding a dopant for adjusting the refractive index, and/or by adjusting the irradiation intensity or the irradiation time of the light, and satisfying the above (1), (2), preferably satisfying the above The cladding layer 12 is under the region near the core of (1) to (3).

Further, when the refractive index is adjusted by adding a dopant, the refractive index depends on the type of the material constituting the lower cladding layer and the type of the dopant, and therefore, in order to obtain the target refractive index, the under cladding is formed according to the composition. The dopant is appropriately selected from the material of the layer.

Since the resin optical waveguide of the present invention is used for connecting the photonic interface of the optical waveguide and the optical fiber with low loss and low cost, it is preferable that the optical signal is made denser by the single-mode optical waveguide. In this case, when the single mode optical waveguide is used for at least one of the wavelengths of 1310 nm and 1550 nm, light can be transmitted with low loss even for the neon waveguide or the single mode fiber, which is preferable.

When the resin optical waveguide of the present invention is used for a photonic interface, the core exposed portion of the resin optical waveguide is connected to the calender waveguide.

[Examples]

Hereinafter, the present invention will be described in further detail by way of examples, but the invention is not limited to the examples.

In the examples shown below, RSoft CAD, manufactured by RSoft Design Group, Inc., defines the construction (size and refractive index) of resin optical waveguides and single-mode fibers, by RSoft Design Group, Inc., which simulates the ‧ engine The manufactured BeamProp (Finite Differential Beam Transfer Method) performs simulation of optical transmission.

Fig. 2 is a schematic view showing a connection portion between a resin optical waveguide and a single mode optical fiber in the embodiment.

(Examples 1~52)

In Examples 1 to 52, Examples 1 to 5, 7 to 11, and Examples 13 to 52 are examples, and Examples 6 and 12 are comparative examples.

The structure of the resin optical waveguide and the single mode fiber is defined by RSoft CAD as shown below.

(single mode fiber 400)

Core 410

Core diameter 8.4μm

Refractive index 1.47

Coating layer 420

Coating diameter 80μm

Refractive index 1.4652

(Resin Optical Waveguide 10)

Single mode optical waveguide

Core 11

Core size 5.9μm in width direction and 2.3μm in length

Refractive index 1.534

Lower cladding layer 12

Thickness 40μm

The refractive index of the interface with the core 11 is 1.52

The region in the vicinity of the core within 10 μm from the core 11 has a refractive index higher on the interface side with the core 11 and a lower refractive index on the far side of the interface with the core 11 Distribution (0 × 10 ^-4 ~ 3.5 × 10 ^-4 / μm).

Upper cladding layer 13

Thickness 40μm

Refractive index 1.52

Core exposed portion 14

Regarding the state in which the core exposed portion 14 is filled with water (refractive index of 1.32) or air (refractive index of 1.00), the connection loss at a wavelength of 1.55 μm is calculated by BeamProp. The results are shown in the following table. Further, in the table, among the refractive indices of the lower cladding layer 12, the refractive index at the interface side with the core 11 is set to n2, and the refractive index at a position of 10 μm from the interface with the core 11 is set. Is n1. Furthermore, n2 is the maximum value of the refractive index n _max of the lower cladding layer 12 in the vicinity of the core, and n1 is the minimum value of the refractive index of the lower cladding layer 12 in the vicinity of the core n _min . The offset Y of the core 11 of the waveguide 10 and the core 410 of the single mode fiber 400 is as shown in FIG. Also, the indicators in the table are as shown in the following table.

Tables 1 to 6 are examples in which the length of the core exposed portion 14 in the light transmission direction is 2000 μm, and Tables 7 and 8 show that the length of the core exposed portion 14 is 500 μm, 1000 μm, 1500 μm, and The result of 3000μm.

As can be seen from the table, the connection loss of Examples 6 and 12 in which the region near the core of the core exposed portion does not have a refractive index distribution is large. On the other hand, the connection loss of Examples 1 to 5, Examples 7 to 11, and Examples 13 to 52, which correspond to the refractive index distribution in the vicinity of the core of the core exposed portion, is 0.00004 μm or more.

Further, as shown in Tables 4 to 6, in the case where the core exposed portion 14 is filled with water or filled with air, the refractive index distribution in the vicinity of the core is 0.00004 μm or more. That is, regardless of the magnitude of the refractive index distribution, and the influence of the offset Y of the core 14 of the optical waveguide 10 and the core 410 of the single mode fiber 400 is less.

(Example 53, Example 54)

Example 53 is an example, and Example 54 is a comparative example. As Example 53, the refractive index of the core was made The resin optical waveguide was 1.53 and the core width was 6.0 μm, the core height was 2.49 μm, the thickness of the upper cladding layer was 24 μm, and the thickness of the lower cladding layer was 50 μm. The core layer side of the lower cladding layer has a refractive index of 1.516 and a refractive index distribution of 0.00008/μm which decreases in refractive index as it leaves the interface of the core. Regarding the refractive index distribution of the lower cladding layer, the region having the upper cladding layer and the region having no upper cladding layer have the same refractive index distribution. The length of the core exposed portion 14 in the light transmission direction was 1750 μm, and the state of the exposed portion of the core was water. The connection loss of the resin optical waveguide and the single mode fiber of Example 53 was 7.0 dB, and the connection loss index was "4".

In Example 54, an optical fiber having the same structure as that of Example 53 was produced except that the refractive index of the lower cladding layer was fixed throughout the thickness direction. The refractive index of the lower cladding layer was fixed at 1.516. The connection loss of the resin optical waveguide of this example 54 to the single mode fiber exceeded 20 dB, and the connection loss index was "1".

The present invention has been described in detail with reference to the specific embodiments thereof, and it is understood that various changes and modifications may be made without departing from the spirit and scope of the invention. The present application is based on Japanese Patent Application No. 2015-154011, filed on Jan.

Claims (11)

A resin optical waveguide characterized in that it has a core body and a refractive index lower than a cladding layer and an upper cladding layer of the core body, and is provided on one end side of the resin optical waveguide The core body and the core exposed portion of the cladding layer adjacent to the core body are exposed, and the portion corresponding to the core exposed portion of the lower cladding layer satisfies the following (1) and (2). The region in the vicinity of the core: (1) the region in the vicinity of the core is a region within a distance of x from the core, and x is 5 μm or more and 20 μm or less; (2) the region near the core has the following refractive index distribution: The refractive index of the interface side of the core is high, and the refractive index with respect to the far side of the interface with the core becomes low. The resin optical waveguide according to claim 1, wherein the length of the core exposed portion in the light transmission direction is 100 μm or more. The resin optical waveguide according to claim 1 or 2, wherein a refractive index distribution of a region in the vicinity of the core is 0.00004 / μm or more. The resin optical waveguide according to any one of claims 1 to 3, wherein a difference between a maximum value n _max of a refractive index of the lower cladding layer in the vicinity of the core body and a minimum value n _min (n _max -n _min ) It is 0.0001 or more. The resin optical waveguide according to any one of claims 1 to 4, wherein a maximum value of the refractive index _n'max in the core and a maximum value of a refractive index of the lower cladding layer in the vicinity of the core are n _max The difference (n' _max -n _max ) is 0.008 to 0.02. The resin optical waveguide according to any one of claims 1 to 5, wherein, in a portion of the lower cladding layer corresponding to the exposed portion of the core, a refractive index of a portion other than the vicinity of the core is a region near the core The minimum value of the refractive index of the lower cladding layer is less than or equal to n _min . The resin optical waveguide according to any one of claims 1 to 6, wherein the resin optical waveguide is a single mode optical waveguide at at least one of a wavelength of 1310 nm and a wavelength of 1550 nm. The resin optical waveguide according to any one of claims 1 to 7, wherein the resin optical waveguide has a core size of 1 to 10 μm. The resin optical waveguide according to any one of claims 1 to 8, wherein the core of the resin optical waveguide comprises a resin containing fluorine. A resin optical waveguide characterized in that it has a core body and a refractive index lower than a cladding layer and an upper cladding layer of the core body, and is provided on one end side of the resin optical waveguide The core body and the core exposed portion of the cladding layer adjacent to the core body are exposed, and the length of the core exposed portion of the resin optical waveguide in the light transmission direction is 500 μm or more, and the lower cladding layer is equivalent to The portion of the exposed portion of the core has a region in the vicinity of the core that satisfies the following (1) to (3): (1) a region in the vicinity of the core in which the distance from the core is within x, and x is 10 μm or more. 20 μm or less; (2) the region near the core has a refractive index distribution: the refractive index on the interface side with the core is high, and the refractive index on the far side of the interface with the core becomes lower; (3) The difference (n _{max -} n _min ) between the maximum value n _max and the minimum value n _min of the refractive index of the lower cladding layer in the vicinity of the core is 0.001 or more. The resin optical waveguide according to any one of claims 1 to 10, wherein the core exposed portion is connected to the pupil waveguide.